Electron-emitting device, electron source, image-forming apparatus, and method for producing electron-emitting device and electron-emitting apparatus

ABSTRACT

A method for producing a durable electron-emitting device having a uniform electron emission characteristic, an electron source, and an image-forming apparatus having a uniform display characteristic for a long period are provided. The method for producing an electron-emitting device according to the present invention includes the steps of: disposing a cathode electrode on a surface of a substrate; providing an electrode opposite the cathode electrode; disposing plural pieces of fiber containing carbon as a main component on the cathode electrode; and applying potential higher than potential applied to the cathode electrode under depressurized condition to an electrode opposite the cathode electrode.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an electronemitting device, anelectron source using therewith, an image-forming apparatus, and amethod for producing an electron-emitting device.

[0003] 2. Related Background Art

[0004] A field emission type (FE-type) electron-emitting device foremitting an electron from a metal surface with a strong field over 10⁶V/cm applied to the metal has attracted attention as one of theeffective cold electron sources.

[0005] If an FE-type cold electron source is put to practical use, athin-type emissive image display device can be realized, therebycontributing to a power saving and lightweight system.

[0006]FIG. 12 shows a vertical FE-type structure. In FIG. 12, referencenumeral 121 denotes a substrate, reference numeral 123 denotes anemitter electrode, reference numeral 124 denotes an insulation layer,reference numeral 125 denotes an emitter, reference numeral 126 denotesan anode, and reference numeral 127 denotes the shape of an electronbeam emitted to the anode. An aperture is formed in the layers of theinsulation layer 124 and a gate electrode 122 arranged on the cathodeelectrode 123. The conical emitter 125 is provided in the aperture (thestructure is hereinafter referred to as a Spindt type structure). Thestructure is disclosed by, for example, C. A. Spindt, “PhysicalProperties of thin-film field emission cathodes with molybdenum cones”,J. Appl. Phys., 47,5248 (1976), etc.

[0007] Furthermore, an example of a lateral FE-type electron-emittingdevice can be formed by an emitter electrode having a pointed end and agate electrode (extracting electrode) for extracting an electron fromthe end of the emitter electrode arranged parallel to the substrate witha collector (referred to as an anode in the present invention) providedin the direction vertical to the opposing direction of the gateelectrode and the emitter electrode.

[0008] An example of an electron-emitting device using a fibrous carbonis disclosed by Japanese Patent Application Laid-Open No. 8-115652,Japanese Patent Application Laid-Open No. 2000-223005, European PatentPublication EP-A1-1022763, etc.

SUMMARY OF THE INVENTION

[0009] In the image-forming apparatus using the above mentioned FE-typeelectron source, an electron beam spot (hereinafter referred to as abeam diameter) can be obtained depending on the distance H from theelectron source to the phosphor, the anode voltage Va between theelectron-emitting device and the phosphor, the device voltage Vf betweenthe cathode electrode and the leading electrode. The above mentionedbeam span is submillimeter, and has sufficient resolution as animage-forming apparatus.

[0010] However, in the image-forming apparatus such as an image displaydevice, etc., resolution with higher precision has been requestedrecently.

[0011] Furthermore, with an increasing number of displayed pixels, powerconsumption has risen from a large device capacity of theelectron-emitting device when it is driven. Therefore, it has beendemanded to reduce the device capacity and the device voltage, andimprove the efficiency of the electron-emitting device.

[0012] Furthermore, it is necessary to have uniform characteristic ofthe electron-emitting device to avoid uneven distribution of thebrightness among the pixels due to the uneven characteristics of theelectronemitting devices.

[0013] As a result, it is requested to reduce the capacity of a device,the device voltage, and the uneven characteristics amongelectron-emitting devices.

[0014] In the Spindt-type electron-emitting device shown in FIG. 12, aparasitic capacity has been formed between a large gate capacity and anumber of emitters 125 by the layer structure of a gate electrode 122and a substrate 121. Furthermore, the device voltage of the spindt-typeFE is as high as several tens of V, thereby causing the problem of largepower consumption from a large capacity.

[0015] Additionally, since extracted electron beams diffuse, a focusingelectrode has been required to suppress the diffusion of the beams. Forexample, Japanese Patent Application Laid-Open No. 07-006714 discloses amethod of focusing the trajectory by providing an electrode for focusingelectrons. However, this method has the problem that the process step ofassigning the focusing electrode is complicated, and that the electronemission efficiency is low.

[0016] Furthermore, since a common horizontal FE is designed such thatan electron emitted from a normal cathode easily crashes against thegate electrode, the efficiency (the ratio of the electric currentflowing through a gate to the electric current reaching the anode) islowered, and the beams largely diffuse at the anode.

[0017] With electron-emitting devices formed by a set of fibrous carbon,local electron emission (electric field concentration) is apparent whenthere are large differences in length and shape among the devices.Therefore, the current density accompanied by the electron emissionbecomes high at a portion where local electric field concentrationarises, thereby possibly deteriorating the electron emissioncharacteristic and shortening the life of the device.

[0018] Additionally, with the image-forming apparatus having a pluralityof the above mentioned devices, the above mentioned events cause theapparent distribution of the amount of le (emission current) of eachelectron-emitting device, thereby reducing the performance of theimage-forming apparatus by resulting in the poor display of gray scaleimages, flickering images, etc.

[0019] The present invention has been developed to solve the abovementioned problems, and aims at providing a durable electron-emittingdevice, electron source, image-forming apparatus having a uniformdisplay characteristic for a long period, and a method for easilyproducing the electron-emitting device and the image-forming apparatusby guaranteeing a uniform electron emission characteristic.

[0020] To attain the above mentioned purpose, the method for producingan electron-emitting device according to the present invention includeson the surface of a substrate the steps of: arranging a cathodeelectrode; arranging an electrode opposite the cathode electrode;arranging a plurality of fibers mainly made of carbon on the cathodeelectrode; and applying higher potential to the electrode opposite thecathode electrode than the potential applied to the cathode electrodeunder the depressurized condition.

[0021] Another method for producing the electron source according to thepresent invention to attain the above mentioned purpose includes thesteps of: arranging on the substrate a plurality of electron-emittingdevices each having a plurality of fibers mainly made of carbon, and aplural pieces of wire each being electrically connected to at least oneof the plurality of electron-emitting devices; applying a voltage to atleast a part of the plurality of electron-emitting devices and measuringthe electric characteristic of the electron-emitting device to which thevoltage has been applied; and reducing the difference in electriccharacteristic among the plurality of electron-emitting devices based onthe measurement result. The step of reducing the difference incharacteristic among the above mentioned plurality of electron-emittingdevices includes the step of allowing electrons to be emitted from atleast one of the plurality of electron-emitting devices under thedepressurized condition.

[0022] Furthermore, it is preferable that the step of emitting anelectron from the above mentioned electron-emitting device is performedunder the condition of a gas physically or chemically reactive to thefiber. In this process, the portion where an electric field concentratesin the fiber is made to be reactive for a partial etching process. As aresult, the stable and uniform electron-emitting device, electronsource, and image-forming apparatus can be produced.

[0023] It is preferable that the gas chemically reactive to the fibercontains H₂, H₂O, O₂, or CO₂. Otherwise, it is desired that the gaschemically reactive to the fiber is a combination of H₂ gas and one ofH₂O, O₂, and CO₂ gas.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIGS. 1A, 1B, 1C, 1D and 1E show a method for producing anelectron-emitting device according to the first embodiment;

[0025]FIGS. 2A and 2B show a step of equalizing the shapes of fineprojections among the electron-emitting devices according to anembodiment of the present invention;

[0026]FIGS. 3A and 3B show an electron-emitting device according to theembodiment of the present invention;

[0027]FIGS. 4A, 4B, 4C and 4D show the step of producing theelectron-emitting device according to the embodiment of the presentinvention;

[0028]FIGS. 5A and 5B show a change with time of an emission current ofan electron-emitting device;

[0029]FIG. 6 shows an example of the configuration when anelectron-emitting device is operated;

[0030]FIG. 7 shows an example of the operation characteristic of anelectron-emitting device according to the embodiment of the presentinvention;

[0031]FIG. 8 shows an example of the configuration of a simple matrixcircuit according to the embodiment of the present invention;

[0032]FIG. 9 shows an example of the configuration of an image-formingapparatus using the electron source according to the embodiment of thepresent invention;

[0033]FIG. 10 shows the outline of the structure of a carbon nanotube;

[0034]FIG. 11 shows the outline of the structure of a graphitenanofiber;

[0035]FIG. 12 shows the conventional vertical FE-type electron-emittingdevice;

[0036]FIG. 13 shows the type of an equalizing process according to thepresent invention; and

[0037]FIG. 14 shows the type of another equalizing process according tothe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] The preferred embodiments of the present invention are describedbelow in detail by referring to the attached drawings. However, thepresent invention is not limited to the dimensions, materials, shapes,and relative arrangements of the components of the embodiments unlessotherwise specified.

[0039] Described first below is the equalizing process of the electronemission characteristic of an electron-emitting device.

[0040] According to the present invention, it is most desirable to usefibrous carbon as an electron-emitting member of an electron-emittingdevice. Since fibrous carbon has a very large aspect ratio, it easilyenhances an electric field. Therefore, it is possible to emit anelectron at a low voltage, and the fibrous carbon is recommended as anelectron-emitting member according to the present invention.

[0041] The “fibrous carbon” according to the present invention can referto a “columnar substance chiefly made of carbon” or “linear substancechiefly made of carbon”. Furthermore, the “fibrous carbon” can also bereferred to as “fiber chiefly made of carbon”. To be more practical, the“fibrous carbon” according to the present invention also includes carbonnanotube, graphite nanofiber, and amorphous carbon fiber. Especially,graphite nanofiber is the most desirable as an electron-emitting member.

[0042] However, when the fibrous carbon is used as an electron-emittingmember, it is frequently used as a set of plural pieces of fibrouscarbon in consideration of the production method. Since it is verydifficult to equalize the shapes of the fibrous carbon in thickness,length, etc., there often occurs unevenness in characteristic among theelectron-emitting devices if the set of plural pieces of fibrous carbonis used as an electron-emitting member of an electron-emitting device.

[0043] Under the situation, according to the present invention, aprocess of reducing the difference in electron emission characteristicamong electron-emitting devices (equalizing process) is performed tocontrol the electron emission characteristic of the electron-emittingdevice in which plural pieces of fibrous carbon is used as anelectron-emitting member.

[0044] The “equalizing process” which is the characteristic of themethod for producing the electron-emitting device according to thepresent invention is performed by applying a voltage to anelectron-emitting device after arranging plural pieces of fibrous carbonon the electrode (cathode electrode) to which potential, which is lowerthan the potential to the opposite electrode (extracting electrode) in apair of electrodes forming the electron-emitting device when the deviceis driven, is applied.

[0045] This method is especially convenient and effective when anelectron source, an image-forming apparatus, etc. are formed using aplurality of electron-emitting devices.

[0046] The “equalizing process” according to the present invention notonly reduces the difference in electron emission characteristic among aplurality of electron-emitting devices, but also improves the electronemission characteristic of one electron-emitting device.

[0047] That is, the electron-emitting device immediately after formingfibrous carbon indicates the difference in shape among plural pieces offibrous carbon. Such a device can form a portion where an electric fieldspecifically concentrates. When such an electron-emitting device havingspecific electric field concentration is operated, electrons are emittedwith concentration from the specific portion, and a load is excessivelygenerated in the portion. As a result, the electron emissioncharacteristic is suddenly damaged, and no sufficient performance of anelectron-emitting device can be obtained.

[0048] Therefore, by performing the “equalizing process” according tothe present invention, the portion in which an electric fieldspecifically concentrates can be removed, and electrons aresubstantially equally emitted from a number of pieces of fibrous carbon(the number of electron emission sites is increased). As a result,electron-emitting devices having an excellent electron emissioncharacteristic and stable for a long period can be obtained.

[0049] It is desired that the above mentioned “equalizing process”according to the present invention is performed by applying a voltage toa device under the condition of a substance reactive to the fibrouscarbon.

[0050] The principle of the equalizing process is performed by anetching operation using the heat generated when an electron is emittedfrom the fibrous carbon, which is an electron-emitting portion, into avacuum. In addition, when the process is performed under the conditionof the substance reactive to fibrous carbon, the reactive substance inthe condition and the fibrous carbon are selectively reactive to eachother, thereby performing a partial etching process.

[0051] Since the fibrous carbon chiefly contains carbon, the followingreactions occur.

C+H₂O→H₂↑+CO↑  (1)

C+O₂→CO₂↑  (2)

2C+O₂→2CO↑  (3)

C+CO₂→2CO↑  (4)

[0052] Therefore, H₂O, CO₂, O₂, H₂, etc. can be useful as substancesreactive to the fibrous carbon.

[0053]FIGS. 2A and 2B shows the type of the equalizing process accordingto the present invention using a lateral electron-emitting device inwhich fibrous carbon is used as an electron-emitting member.

[0054] In FIGS. 2A and 2B, reference numeral 1 denotes an insulatingsubstrate, reference numeral 2 denotes a extracting electrode (alsoreferred to as a “second electrode” or “gate electrode”), referencenumeral 3 denotes a cathode electrode (also referred to as a “firstelectrode” or “negative electrode”), reference numeral 4 denotes anelectron-emitting member comprising plural pieces of fibrous carbonelectrically connected to the cathode electrode. Reference numeral 20denotes a vacuum chamber, reference numeral 21 denotes a substrateholder, reference numeral 22 denotes a gas leading valve, referencenumeral 23 denotes vacuum pump, reference numeral 24 denotes an anode(also referred to as a “third electrode”), and reference numeral 25denotes an equipotential surface.

[0055] In this example, a lateral electron-emitting device is described,but the producing method according to the present invention is alsoapplicable to a vertical electron-emitting device in which fibrouscarbon is used as an electron-emitting member. Furthermore, since alateral electron-emitting device is simpler in production, and smallerin capacity in the driving operation than the vertical electron-emittingdevice, a high-speed driving process can be performed.

[0056] Furthermore, although the vertical electron-emitting device shownin FIG. 12 includes a cathode electrode 123 and an extracting electrode(gate electrode) 125, the fibrous carbon can emit electrons in a lowelectric field. Therefore, the present invention can also be applied toa vertical electron-emitting device without a gate electrode 125 and aninsulating layer 124 shown in FIG. 12. That is, the present inventioncan be applied to an electron-emitting device configured by the cathodeelectrode 123 provided on the substrate 121 and fibrous carbon providedthereon.

[0057] In the vertical electron-emitting device, an “equalizing process”can be performed by performing the voltage applying process similar tothe process performed in the “equalizing process” described later, forapplying the voltage between the cathode electrode (reference numeral123 shown in FIG. 12) where the fibrous carbon is arranged and the anode(reference numeral 126 shown in FIG. 12). Otherwise, an “equalizingprocess” can also be performed by performing the process similar to thevoltage applying process performed in the “equalizing process” describedlater, for applying the voltage between the extracting electrode(reference numeral 122 shown in FIG. 12) and the cathode electrodeprovided between the cathode electrode (reference numeral 123 shown inFIG. 12) where the fibrous carbon is arranged and the anode (referencenumeral 126 shown in FIG. 12).

[0058] Furthermore, an “equalizing process” can also be performed byarranging an electrode plate above the cathode electrode where thefibrous carbon is provided, and performing a voltage applying processsimilar to the voltage applying process performed in the “equalizingprocess” described later between the electrode plate and the cathodeelectrode.

[0059] The “equalizing process” introduces an “reactive gas” reactive tothe fibrous carbon from the gas leading valve 22 after evacuating thevacuum chamber 20 by the vacuum pump 23. Then, a voltage is applied tothe electron-emitting member 4 of fibrous carbon such that theextraction electrode 2 can be positive, and an electron is emitted fromthe electron-emitting member 4 of fibrous carbon. Then, theelectron-emitting member 4 of fibrous carbon proceeds with the abovementioned reaction toward right by means of the heat from the electronemission, etc., thereby etching the fibrous carbon (FIG. 2A).

[0060] During the process of the above mentioned reaction, the reactivegas on the left side is incessantly introduced by the gas leading valve22, the product on the right is evacuated by the vacuum pump 23, and theabove mentioned reaction expressions are proceeding right.

[0061] Since the reaction can be reciprocal, a reaction product is setto be immediately removed from the reaction system.

[0062] Furthermore, it is recommended to reserve the time to stopelectron emission to promote the reaction between the reactive gas andthe electron-emitting member. To attain this, it is desired that a pulsevoltage is applied between the electron-emitting member 4 and theextraction electrode 2.

[0063] Since the reaction is driven by the heat from the electronemission, the portion of the electron-emitting member 4 easily emittingan electron (in which an electric field can be easily enhanced) reactswith concentration to the heat and then be etched in the set of fibrouscarbon. As a result, the electric field can be equally applied by anelectron emission area by removing the portion where the electric fieldhas excessively been concentrated.

[0064]FIG. 2B shows the type of the result of the “equalizing process”.After performing the “equalizing process”, the electric field differenceapplied to each piece of fibrous carbon is reduced. That is, theequipotential surface 25 which is largely distorted as shown in FIG. 2Ais reduced in distortion as shown in FIG. 2B.

[0065] When an image-forming apparatus is provided, etc., the“equalizing process” can also be performed after bonding an electronsource substrate formed by a plurality of electron-emitting devices eachhaving fibrous carbon and the wiring for use in driving theelectron-emitting devices with a face plate having an image-formingmember comprising a phosphor, etc., and forming a vacuum envelope(referred to as a sealing process).

[0066] In the above mentioned process, the performance of theelectron-emitting device, electron source, and image-forming apparatususing plural pieces of fibrous carbon can be improved.

[0067] That is, the electron-emitting device according to the presentinvention prevents the local electric field concentration in the“equalizing process”, thereby equalizing the electron emissioncharacteristic, and suppressing the attenuation of the emission currentby the overload from the high current density due to the local fieldconcentration.

[0068] Therefore, the induction of discharge can be suppressed, thedurability of the electron-emitting device can be elongated, and astable electron emission current with small fluctuations with time canbe maintained.

[0069] Then, since the electron emission current of eachelectron-emitting device can be stably maintained in the electron sourceand the image-forming apparatus including a plurality ofelectron-emitting devices, the durability of each pixel can be improved,the gray scale of an image can be successfully expressed, and theflicker of the image can be avoided, thereby expressing equal displaycharacteristic for a long period.

[0070] Described below is an embodiment of the practical configurationaccording to the present invention.

[0071]FIGS. 3A and 3B show an example of the configuration of theelectron-emitting device on which the producing method according to thepresent invention works. FIG. 3A is a plan view of the electron-emittingdevice according to the present embodiment. FIG. 3B is a sectional viewalong 3B-3B shown in FIG. 3A.

[0072] In FIGS. 3A and 3B, reference numeral 1 denotes a substrate,reference numeral 2 denotes an extracting electrode, reference numeral 3denotes a cathode electrode, and reference numeral 4 denotes anelectron-emitting member. FIGS. 4A to 4D schematiclly show a type of themethod of producing an electron-emitting device according to the presentembodiment. An example of the method of producing an electron-emittingdevice according to the present embodiment is described below byreferring to FIGS. 4A to 4D.

[0073] The substrate 1 refers to quartz glass, glass whose impurecontents such as Na, etc. are reduced and replaced with K, etc.,sodalime glass, a layer structure obtained by applying SiO₂ on thesilicon substrate, etc. in the spatter method, etc., and an insulatingsubstrate such as ceramics, etc. of alumina, etc. (FIG. 4A).

[0074] The extraction electrode (gate electrode) 2 and the cathodeelectrode 3 are disposed on the insulating substrate 1 (FIG. 4B).

[0075] The extraction electrode 2 and the cathode electrode 3 areconductive, and can be formed by the common vacuum film-formingtechnology such as the evaporation method, the spatter method, etc. andthe photolithography technology.

[0076] The material of the extraction electrode 2 and the cathodeelectrode 3 can be, for example, carbon, metal, metal nitride, metalcarbide, metal boride, semiconductor, or metal compound semiconductor.

[0077] The thickness of the electrodes 2 and 3 can be set in the rangefrom several tens nm to several pm. It is desired to use such a heatresistant material as carbon, metal, metal nitride, metal carbide, etc.If the potential can be reduced due to a thin electrode, or if theelectron-emitting device is used in a matrix array, then a lowresistance metal wiring material can be used in a portion not involvedin the electron emission as necessary.

[0078] The distance between the extraction electrode 2 and the cathodeelectrode 3 can be determined depending on the device voltage drivingthe electron-emitting device between the extraction electrode 2 and thecathode electrode 3 such that the electron emission field can be onethrough ten times larger than the vertical field when the electronemission field (lateral field) of the electron-emitting member 4 iscompared with the vertical field required to form an image.

[0079] For example, when the distance between the anode 24 and thecathode electrode 3 is 2 mm, and 10 kV is applied, the vertical field is5 V/μm. In this case, the distance and the device voltage are to bedetermined such that the electron emission field of theelectron-emitting member to be used is larger than 5 V/μm, andcorresponds to be the selected electron emission field.

[0080] The “lateral field” according to the present invention can bereferred to as a “electric field practically parallel to the surface ofthe substrate 1”, or a “electric field in the direction of theextraction electrode 2 opposite the cathode electrode 3.

[0081] The “vertical field” according to the present invention refers toan “electric field in the direction substantially perpendicular to thesurface of the substrate 1”, or an “electric field in the direction ofthe substrate 1 opposite an anode electrode 61”.

[0082] Then, the electron-emitting member 4 having an uneven surface isdisposed on the cathode electrode 3 (FIG. 4C). The material used as theelectron-emitting member 4 is a set of fibrous carbon. It is desiredthat the fibrous carbon is graphite fiber.

[0083] The above mentioned fibrous carbon has a threshold field ofseveral V/μm. FIGS. 10 and 11 show an example of configurations offibrous carbon suitable for the present invention. Each figure shows anembodiment at an optical microscope level (approximately 1000×) on theleft, an embodiment at a scanning electronic microscope (SEM) level(approximately 30,000×) in the center, and an embodiment at atransmission electronic microscope (TEM) level (approximately 1millions) on the right.

[0084] As shown in FIG. 10, a cylindrical shape of graphen (multiplewall cylinder is referred to as a multiwall nanotube) is referred to asa carbon nanotube, and its threshold is the smallest when the tip of thetube is opened.

[0085]FIG. 11 shows the fibrous carbon may be produced at a relativelylow temperature. A fibrous carbon of this form is comprised of alamination of graphens (which is thus sometimes called “graphitenanofiber” and the ratio of the amorphous structure of which increasesdepending on the temperature). To be more practical, the graphitenanofiber indicates a fibrous substance in which graphens are layered(laminated) in the longitudinal direction (axial direction of fiber).That is, as shown in FIG. 11, it is a fibrous substance in whichplurality of graphens are arranged and layered (laminated) so as not tobe parallel to the axis of the fiber.

[0086] The other carbon nanotube is a fibrous substance in whichgraphens are arranged (in cylindrical shape) around the longitudinaldirection (axial direction of fiber). In other words, it is a fibroussubstance in which graphens are arranged substantially in parallel tothe axis of the fiber.

[0087] One sheet of graphite is referred to as a “graphen” or a “graphensheet”. To be more practical, graphite is obtained by laying pluralcarbon sheets, a lamination in which carbon planes, each of which is aspread of regular hexagons consisting of covalent bonds of carbon atomsin sp² hybrid, are layered at intervals of distance of 3.354 Å. Each ofthe carbon planes is called a “graphen” or a “graphen sheet”.

[0088] Either fibrous carbon has an electron emission threshold of 1 Vto 10 V/μm and is recommendable as the material of the emitter(electron-emitting member) 4.

[0089] Especially, an electron-emitting device using a set of graphitenanofiber is not limited to the device structure according to thepresent invention shown in FIGS. 2 and 3, but can emit electrons in alow electric field, can obtain a large emission current, can be easilyproduced, and obtains an electron-emitting device having a stableelectron emission characteristic. For example, a graphite nanofiberemitter is used, an electron-emitting device can be obtained bypreparing an electrode for controlling the electron emission from theemitter, and a light emitting apparatus such as a lamp, etc. can beformed using a light emission member emitting light by the irradiationof an electron emitted from a graphite nanofiber. Furthermore, byarranging plural arrays of electron-emitting devices using the abovementioned graphite nanofiber and by preparing an anode electrodecomprising a light emission member such as a phosphor, etc., animage-forming apparatus such as a display, etc. can be configured. Anelectron-emitting device, a light emitting device, and an image-formingapparatus using graphite nanofiber can stable emit electrons withoutkeeping the inside each device in a vacuum state as in the conventionalelectron-emitting device. Furthermore, since electrons can be emitted ina low field, a reliable device can be easily produced. As a result, theproducing method according to the present invention is morerecommendable in the device using the graphite nanofiber.

[0090] The above mentioned fibrous carbon can be formed by decomposingthe hydrogen carbide gas using a catalyst (a material for promoting thepile of carbon). The carbon nanotube and the graphite nanofiber dependon the type of catalyst and the temperature of decomposition.

[0091] As the catalyst material, Fe, Co, Pd, Ni, or an alloy of any ofthe selected materials can be used as the nucleus forming the center ofthe fibrous carbon.

[0092] In particular, Pd, Ni may be material for generating graphitenanofiber at a low temperature (400° C. or more). The temperature atwhich the carbon nanotube is generated using Fe or Co is over 800° C.while the graphite nanofiber material can be generated at a lowtemperature. Therefore, it is desired from the viewpoint of theinfluence on other members and the production cost to generate graphitenanofiber material using Pd and Ni.

[0093] Furthermore, relating to Pd, using the characteristic of an oxidewhich is reduced at a low temperature (room temperature), paradium oxidecan be used as a nucleus forming material.

[0094] When a hydrogen reduction process is performed on a paradiumoxide, a fast condensation nucleus can be formed at a relatively lowtemperature (200° or lower) without thermal condensation of a thin metalfilm or generation and evaporation of super-particle conventional usedas common nucleus forming technology.

[0095] The above mentioned hydrogen carbide gas can be, for example,ethylene, methane, propane, propylene, CO, CO₂ gas, or vapor of anorganic solvent such as ethanol, acetone, etc.

[0096] Furthermore, the present invention can be applicable to anyelectron-emitting member 4 having an uneven surface as shown in FIG. 4C.The material of the electron-emitting member 4 having an uneven surfacecan be a heat-resistant material such as W, Ta, Mo, etc., a carbide suchas TiC, ZrC, HfC, TaC, SiC, WC, etc., a boride such as HfB₂, ZrB₂, LaB₆,CeB₆, YB₄, GdB₄, etc., a nitride such as TiN, ZrN, HfN, etc., asemiconductor such as Si, Ge, etc., carbon and carbon compound, etc.containing diffused amorphous carbon, graphite, diamond-like carbon, anddiamond.

[0097] Such a electron-emitting member 4 having an uneven surface can beobtained by either the process of generating projections using a methodof the RIE, etc. from a film piled in the common vacuum film-formingmethod, etc. such as the spatter method, etc. or the process of growinga pin-shaped crystal through the generation of a nucleus in the CVD,growing a whisker-shaped crystal, etc.

[0098] The control of the shape of the projections depends on the typeof substrate to be used, the type of gas, the pressures of a gas (flowrate), an etching time, the energy when plasma is formed, etc. On theother hand, in the CVD forming method, control is performed based on thetype of substrate, the type of gas, the flow rate, the growingtemperature, etc.

[0099] Regardless of the relation to the electron emission, the area inwhich the electron-emitting member 4 is placed is referred to as an“electron emission area” according to the present invention.

[0100] Then, the above mentioned electron-emitting member 4 is partiallyetched, and the “equalizing process” increasing the number of emissionsites is performed (FIG. 4D).

[0101] After the electron-emitting device is provided in the vacuumchamber 20 as shown in FIGS. 2A and 2B, and the vacuum chamber 20 isevacuated by the vacuum pump 23, the gas leading valve 22 introduces asubstance chemically or physically reactive to the electron-emittingmember 4.

[0102] A chemically reactive substance can be the above mentioned O₂,CO, H₂O, H₂, etc. when the electron-emitting member 4 is carbon (fibrouscarbon). It is preferable that the gas chemically reactive to the fiberis a mixed gas of a gas selected from among H₂O, O₂, CO₂ and H₂ gasses.

[0103] A substance physically reactive refers to a substance which canbe an electrified particle when an electron beam crashes, and it isdesired to have a substance having a large mass such as Ar, etc. Theintroduction pressure of a gas of the above mentioned substance dependsof the type of gas. However, when the substance is chemically reactive,it is 1×10⁻⁴ Pa or over. When the substance is physically reactive, itis approximately 1×10⁻⁶ to 1×10⁻⁴ Pa.

[0104] If potential is applied to the electron-emitting member 4 of theelectron-emitting device such that the extraction electrode 2 of theelectron-emitting device can be positive, and an electron is emittedafter introducing the above mentioned gas, then the above mentioned gasis reactive to the electron-emitting member 4 to etch theelectron-emitting member 4.

[0105] In this step in the electron emission area, a portion in whichelectrons can be easily emitted (an electric field can be easilyenhanced) becomes reactive and etched with concentration, a portion inwhich an electric field has excessively concentrated can be removed, andthe field can be more equally applied to the electron emission area.

[0106]FIGS. 2A and 2B show the type of this process. FIG. 2A shows thetype of the device when the “equalizing process” is started, and FIG. 2Bshows the type of the device after performing the “equalizing process”.

[0107] When an image-forming apparatus is formed, this step can also beperformed by: bonding the electron source substrate on which wiring,etc. is arranged for an electron-emitting device to the face platehaving an image-forming member comprising a phosphor, etc.; introducingthe reactive gas after forming an envelope (referred to a sealing step);and applying positive potential to the anode in the electron emissionarea.

[0108] Thus, an electron-emitting device according to the presentembodiment can be formed.

[0109] The electron-emitting device and its operation obtained in theabove mentioned steps are described below by referring to FIGS. 6 and 7.An electron-emitting device having a gap of several pm between theextraction electrode 2 and cathode electrode 3 is provided in a vacuumchamber 60 as shown in FIG. 6 to allow a vacuum pump 63 to completelyperform an evacuation until achieving a pressure of about 10⁻⁵ Pa, theanode electrode 61 is provided at the height of H, which if several mmfrom the substrate 1, using a high voltage as shown in FIG. 6, and ananode voltage Va, that is, a high voltage of several kV, is appliedbetween the cathode electrode 3 and the anode electrode 61.

[0110] A phosphor 62 coated with a conductive film is provided on theanode electrode 61.

[0111] A device voltage Vf of a pulse voltage of several tens V isapplied between the extraction electrode 2 and the cathode electrode 3to measure a flowing device current If and an electron emission currentIe.

[0112] At this time, an equipotential line 66 is formed as shown in FIG.6, and the point at which an electric field concentrates is locatedclosest to the anode 61 of the electron-emitting member 4 indicated by64, and inside the gap.

[0113] It is assumed that an electron is emitted from theelectron-emitting member 4 located near the electric field concentrationpoint 64.

[0114] As shown in FIG. 7, the characteristic of the electron emissioncurrent Ie of the electron-emitting device shows Ie suddenly risingabout half of the applied voltage (device voltage Vf), If having thecharacteristic similar to that of Ie, but having a sufficiently smallervalue than Ie.

[0115] Furthermore, Ie observed when the electron-emitting member 4 isdestroyed, etc. due to the local field concentration on theelectron-emitting member 4 has not suddenly fluctuated.

[0116]FIG. 5A shows the Ie fluctuation when each of the devices A, B,and C according to the present embodiment produced in the same producingmethod is driven with Vf, Va, and H set constant. It proves that thethree devices A, B, and C indicate small fluctuation, and have similarIe values.

[0117] For comparison, FIG. 5B shows the fluctuation of Ie (emissioncurrent) when each of the devices D, E, and F produced in the sameproducing method except omitting the equalizing process (shown in FIG.4D) by the electron-emitting member 4 is driven. In the device D, asudden drop of Ie is observed in the driving period. In the device F, Ieis stepwise reduced, and indicates a saturation tendency at a certainvalue. Ie of the device E is stable.

[0118] Thus, without performing the “equalizing process”, thecharacteristic of devices are unequal because the devices have differentportions where an electric field easily concentrates due to differentconfigurations of fibrous carbon which is an electron-emitting member.

[0119] Listed below are examples of three devices (A, B, and C), anddescribed below is an example of an equalizing process among a number ofdevices according to the present invention. FIG. 14 shows electronemission characteristics of different devices A to C before the“equalizing process”.

[0120] In this example, the threshold V_(th3) of the electron emissionis largest for the device C, and the threshold V_(th1) of the electronemission is smallest for the device A.

[0121] When the device A is driven with a pulse voltage under thecondition of the above mentioned reactive gas, the mechanism of theabove mentioned chemical etching of carbon suddenly reduces the electronemission current of the device A. The process is performed with thevoltage applied to the device A gradually increased until the electronemission cannot be substantially detected when the threshold voltage(V_(th3)) of the device c is obtained. Similarly, the process isperformed on the device B until the current value is reduced from thevalue indicated by the point A shown in the figure to the valueindicated by the point B.

[0122] Thus, if the characteristic of each device is evaluated under thecondition after the reactive gas has been evacuated, the electronemission characteristics of the devices A and B can substantially matchthe electron emission characteristic of the device C.

[0123] A preferable method as the “equalizing process” among a number ofdevices is described below. The preferable method comprising the stepsof: find the electron-emitting device whose threshold voltage requiredto emit an electron is determined to be low with the characteristic ofother devices, and then make the threshold voltages of the other devicesbecomes closer to the threshold of the device whose threshold voltage isdetermined to be low with the other devices.

[0124] An example of the method for performing the equalizing process onan electron source for which a plurality of electron-emitting devicesare provided is described below by referring to FIG. 8 based on theabove mentioned principle. In FIG. 8, reference numeral 81 denotes anelectron source substrate, reference numeral 82 denotes X directionwiring, reference numeral 83 denotes Y direction wiring, referencenumeral 84 denotes an electron-emitting device, and reference numeral 85denotes a connection line.

[0125] X direction wiring 82 is formed by m pieces of wiring, that is,Dx1, Dx2, . . . , Dxm, and can be configured by conductive metal, etc.formed in the vacuum evaporation method, the printing method, thespattering method, etc. The material, the film thickness, the width ofthe wiring can be appropriately designed.

[0126] The Y direction wiring 83 is formed by n pieces of wiring, thatis, Dy1, Dy2, . . . , Dyn, which is similarly formed in the X directionwiring 82.

[0127] Among the m pieces of X direction wiring 82 and n pieces of Ydirection wiring 83, an inter-layer insulation layers (not shown in theattached drawings) for separating them, which layers separate bothelectrically.

[0128] The inter-layer insulation layer not shown in the attacheddrawings is configured by SiO₂, etc. formed in the vacuum evaporationmethod, the printing method, the spattering method, etc. For example, itis formed in a desired shape on all or a part of the electron sourcesubstrate 81 on which the X direction wiring 82 is arranged. Its filmthickness, material, and producing method are appropriately designed tostand the potential difference at the crossing portion between the Xdirection wiring 82 and the Y direction wiring 83.

[0129] The X direction wiring 82 and the Y direction wiring 83 are ledas external terminals.

[0130] A pair of electrodes (not shown in the attached drawings) formingthe electron-emitting device 84 are electrically connected by m piecesof the X direction wiring 82, n pieces of the Y direction wiring 83, andthe connection line 85 comprising conductive metal, etc.

[0131] When the number of rows in the X direction and the number ofcolumns in the Y direction increase in the simple matrix as shown inFIG. 8, there occurs apparent distribution of the voltage applied toeach device due to a drop of voltage if the “equalizing process” iscollectively performed by selecting all of the electron-emitting devices84 in the matrix. For example, it is desired that the “equalizingprocess” is performed with line (wiring) by line (wiring) or the“equalizing process” is performed with one by one (dot sequentially).

[0132] In this embodiment, an example of the equalizing processperformed on all electron-emitting devices is described. However, theequalizing process can be performed not on all electron-emittingdevices, but only on a desired electron-emitting device.

[0133] Before performing the equalizing process, it is desired that theelectric characteristic of the electron-emitting device 84 is measured.It can be determined how the electric characteristic of eachelectron-emitting device can be set based on the data obtained in themeasurement. The electric characteristic to be measured (monitored) isobtained by measuring the current occurring when a predetermined voltageis applied to each electron-emitting device or between theelectron-emitting device and the anode.

[0134] A current occurring in an electron-emitting device can be acurrent flowing between an extraction electrode and a cathode electrodewhen a predetermined voltage is applied between the extraction electrodeand the cathode electrode of each electron-emitting device. A currentoccurring between the anode electrode and the electron-emitting devicecan be a current detected when a current flowing to anode (emissioncurrent from the electron-emitting device) when a predetermined voltageis applied between the anode electrode and the electron-emitting device.

[0135] It is desired that the measurements of the electriccharacteristic are made on all electron-emitting devices. However, whenthe number of electron-emitting device increases, measurements can bemade only on limited devices, and the “equalizing process” can beperformed based on the measurement value.

[0136] To have the electric characteristics of all electron-emittingdevices close to a predetermined value range based on the measuredelectric characteristic, it is desired to perform the “equalizingprocess” on all electron-emitting devices. However, if the electriccharacteristics of devices are not quite different from each other, the“equalizing process” can be performed only on the electron-emittingdevice having the characteristic out of the desired range.

[0137] Described below is the above mentioned method of sequentiallyequalizing lines. For example, the “equalizing process” is performed bycommonly connecting (for example, a GND connection) n pieces of Ydirection wiring, that is, Dy1, Dy2, . . . , Dyn, applying positivepotential to the Y direction wiring to Dx1 of the X direction wiring,and selecting the electron-emitting device at the row Dx1(electron-emitting device connected to the wiring of Dx1) 84. Then, asimilar voltage is applied to Dx2, the electron-emitting device at therow Dx2 is selected, and the “equalizing process” is performed.Similarly, the rows Dx3, Dx4, . . . , Dxm are sequentially selected, andthe equalizing process is performed in the X direction in a linesequence. Thus, the influence of a voltage drop can be reduced. In thisembodiment, the “Tequalizing process” is performed on allelectron-emitting devices connected to one piece of X direction wiring.However, the “equalizing process” can be performed on some of theelectron-emitting devices connected to one pieces of the X directionwiring. That is, the “equalizing process” is not performed on allelectron-emitting devices, but can be performed only on desiredelectron-emitting devices.

[0138] Then, in the “equalizing process” sequentially performed one(device) by one (device), each device is selected using the abovementioned matrix wiring using the above mentioned matrix wiring so thatit can be independently driven, and the electron-emitting device 84 canbe individually equalized. In this method, there is no influence of avoltage drop, but the time required to perform the process isproportional to the number of the devices. Therefore, any of the linesequence process, the point sequence process, and a collective processcan be performed depending on the size or the use of an electron source.Also in this method, the equalizing process is not performed on allelectron-emitting devices, but is performed only on desiredelectron-emitting devices.

[0139] Described below is the image-forming apparatus configured usingthe electron source of the above mentioned simple matrix by referring toFIG. 9. FIG. 9 shows a type of an example of the display panel of theimage-forming apparatus.

[0140] In FIG. 9, reference numeral 81 denotes an electron sourcesubstrate 81 for which a plurality of electron-emitting devices areprovided, reference numeral 91 denotes a rear plate to which theelectron source substrate 81 is fixed, reference numeral 96 denotes aface plate in which a fluorescent film 94, a metal back 95, etc. areformed inside a glass substrate 93. Reference numeral 92 denotes asupport frame to which the rear plate 91 and the face plate 96 arebonded using frit glass, etc. Reference numeral 97 denotes an envelopecan be formed and sealed by baking at the temperature of 400 to 500° C.for over 10 minutes in the vacuum or nitrogen.

[0141] As described above, the envelope 97 comprises the face plate 96,the support frame 92, and the rear plate 91. Since the rear plate 91 isprovided mainly to reinforce the strength of the electron sourcesubstrate 81, the separate rear plate 91 is not required if the electronsource substrate 81 itself is strong enough. That is, the support frame92 can be bonded directly to the electron source substrate 81 so thatthe face plate 96, the support frame 92, and the electron sourcesubstrate 81 can configure the envelope 97. On the other hand, a supportunit, referred to as a spacer, not shown in the attached drawings can beprovided between the face plate 96 and the rear plate 91 to configurethe envelope 97 durable against the atmosphere.

[0142] Furthermore, the “equalizing process” of the electron-emittingmember 4 according to the present embodiment can be performed byintroducing a reactive gas using a gas lead tube 98 after forming theenvelope 97. The lead gas and the reaction product can be removed at anytime by an evacuation tube 99.

[0143] The image-forming apparatus according to the present embodimentcan also be used as an image-forming apparatus, etc. as a display devicesuch as a device for a television broadcast, video conference system, acomputer, etc. and an optical printer configured by a photosensitivedrum, etc.

[0144] (Embodiments)

[0145] Described below in detail are practical embodiments according tothe present invention.

[0146] (First Embodiment)

[0147] As the first embodiment of the present invention, an electron isemitted between the cathode electrode and the extraction electrode ofthe electron-emitting device under the condition of an O₂ gas, and the“equalizing process” is performed. FIGS. 1A to 1E show a method ofproducing an electron-emitting device according to the presentembodiment. FIGS. 3A and 3B are a plan view and a sectional view of theproduced electron-emitting device. Described below is the step ofproducing the electron-emitting device according to the presentembodiment.

[0148] (Step 1 (FIG. 1A))

[0149] A quarts substrate is cleaned and used as the substrate 1. 5 nmthick Ti and 30 nm thick Pt area are continuously evaporated in thespatter method as the extraction electrode 2 and the cathode electrode3.

[0150] Then, in the photolithography process, a resist pattern is formedusing a positive type photoresist (AZ 1500 made by Clariant).

[0151] Next, the Pt layer and Ti layer dry etching processes areperformed using Ar with the patterned photoresist as a mask, and theextraction electrode 2 and the cathode electrode 3 having the gap of 5pm between the electrodes are formed.

[0152] (Step 2 (FIG. 1B))

[0153] Then, about 100 mm thick Cr is piled in the evaporating process.In the photolithography process, a resist pattern is formed using apositive type photoresist (AZ 1500 made by Clariant).

[0154] Next, using the patterned photoresist as a mask, the area (100 μmsquare) for coating the electron-emitting member 4 is formed on thecathode electrode 3, and the Cr of an aperture is removed by a ceriumnitrate etching solution.

[0155] After removing the photoresist, a complex solution obtained byadding a Pd complex to isopropyl alcohol, etc. is applied by a spincoat.

[0156] After the application, a heat treatment is performed at 300° C.in the atmosphere, about 10 nm thick palladium oxide 41 is formed on thecathode electrode 3, and then Cr is removed by the cerium nitrateetching solution.

[0157] (Step 3 (FIG. 1C))

[0158] The atmosphere is evacuated with the heat of 200° C., the heattreatment is performed in the flow of the 2% hydrogen diluted bynitrogen. At this step, an about 3 to 10 nm diameter particle 42 isformed on the surface of the cathode electrode 3. At this time, thedensity of the particle 42 is estimated to be about 10¹¹ to 10¹²/cm².

[0159] (Step 4 (FIG. 1D))

[0160] Then, in the flow of 0.1% ethylene diluted by nitrogen, the heattreatment is performed at 500° C. for 10 minutes. When this process isobserved by a scanning electronic microscope, it proves that a number ofpieces of fibrous carbon 43 extending as 10 to 25 nm diameter curvingfiber are formed on the Pd coated area. At this time, the fibrous carbon43 is about 500 nm thick.

[0161] (Step 5 (FIG. 1E))

[0162] Then, a device is provided in the vacuum device 20 shown in FIGS.2A and 2B, the vacuum pump 23 performs the evacuation up to 1×10⁻⁵ Pa,the gas leading valve 22 leads an O₂ gas until the vacuum level in thevacuum device 20 reaches 1×10⁻⁴ Pa, and a pulse voltage is applied tothe cathode electrode 3 with the extraction electrode 2 set positive.The system is driven for 1 hour in this state, and the electron-emittingmember 4 is equalized.

[0163] The electron-emitting device is formed in the above mentionedsteps, and completely evacuated by the evacuation device 63 in thevacuum device 60 shown in FIG. 6 until 2×10⁻⁶ Pa is reached, and ananode voltage Va=10 kV is applied to the anode electrode 61 H=2 mm apartas shown in FIG. 6.

[0164] At this time, a pulse voltage of device voltage Vf=20 V isapplied to the electron-emitting device, and the flowing device currentIf and the electron emission current Ie are measured.

[0165] The Ie characteristic of the electron-emitting device shows asudden increase of Ie from the half of the applied voltage, and theelectron emission current Ie of about 1 μA is measured with Vf of 15 V.Thus, a preferable electron emission characteristic can be obtained witha small fluctuation of Ie with time.

[0166] On the other hand, If is similar to the characteristic of Ie, andthe value is smaller than the value of Ie by one digit.

[0167] The mechanism of the equalizing process according to the presentembodiment is described below by referring to FIG. 13. FIG. 13 shows achange in device characteristic before and after the equalizing process.

[0168] The electron-emitting device before the equalizing process showsthe characteristic of emitting an electron at the threshold V_(th1)(about 1 V/μm). Then, as described above, when a pulse voltage isapplied to the device in the O₂ gas, the electron emission current ofthe device is suddenly reduced by the mechanism of the chemical etchingof the above mentioned carbon. The voltage applied to the device isgradually increased, and the process is performed until no emission isemitted at the threshold voltage of V_(th 2).

[0169] When the device characteristic is evaluated after evacuating theO₂ gas, the characteristic has been changed such that an electron isemitted at the threshold of V_(th2). At this time, it is assumed thatthe fluctuation width of the electron emission current obtained by theelectron emission has been reduced, and the number of electron emissionpoints has increased in the equalizing process.

[0170] The diameter of an electron beam emitted from the device obtainedaccording to the present embodiment is long in the Y direction and shortin the X direction, that is, substantially rectangular.

[0171] (Second Embodiment)

[0172] An example of the equalizing process performed by emitting anelectron as biased between the cathode electrode of theelectron-emitting device and the anode opposing the electron-emittingdevice in the O₂ gas in the second embodiment.

[0173] (Step 1)

[0174] In the method similarly used in the steps 1 to 4 according to thefirst embodiment, the extraction electrode 2 and the cathode electrode 3are formed on the substrate 1, and fibrous carbon is produced as theelectron-emitting member 4 on the substrate 1.

[0175] (Step 2)

[0176] The electron-emitting device is provided for the vacuum device 20as shown in FIGS. 2A and 2B, the evacuation device 23 performs theevacuation process until 2×10⁻⁶ Pa is reached, the gas leading valve 22leads the O₂ gas until the vacuum level in the vacuum device 20 reaches1×10−4 Pa, and the pulse voltage of Vf=20 V (with the pulse width of 10msec and the pulse length of 4 msec) is applied to the cathode electrode3 of the electron-emitting device with the extraction electrode 2 of theelectron-emitting device set positive. Simultaneously, a voltage ofVa=10 kV is applied to the anode 24. The system is operated in thisstate for 1 hour, and the electron-emitting member 4 is equalized.

[0177] The electron-emitting device produced as mentioned above is fixedto the Vr of 15 V, the inter-anode distance H is fixed to 2 mm, and thedevice is driven with the anode voltage Va of 10 kV. With theconfiguration, a stable Ie can be obtained as in the first embodiment.

[0178] (Third Embodiment)

[0179] An example of the equalizing process performed for each line of amatrix in the display device comprising a matrix electron source inwhich a plurality of electron-emitting devices are provided is describedbelow by referring to FIGS. 8 and 9.

[0180] In FIG. 8, reference numeral 81 denotes an electron sourcesubstrate, reference numeral 82 is X direction wiring, and referencenumeral 83 is Y direction wiring, reference numeral 84 denotes anelectron-emitting device, and reference numeral 85 denotes a connectionline.

[0181] When the device capacity of a plurality of devices increases, thewaveform becomes unclear by the capacity elements although a short pulseaccompanied by the pulse width modulation is added in the matrix wiringas shown in FIG. 8, and the problem that an expected gray scale cannotbe obtained, etc. occurs.

[0182] Therefore, according to the present embodiment as in the firstembodiment, an inter-layer insulation layer is provided close to theelectron-emitting member 4, thereby reducing the increase by thecapacity element outside the element emission area.

[0183] In FIG. 8, the X direction wiring 82 comprises m pieces ofwiring, that is, Dx1, Dx2, . . . , Dxm, and comprises about 1 μm thickand 300 μm wide aluminum wiring material formed in the evaporationmethod. The material, thickness of film, and width of the wiring areappropriately designed.

[0184] The Y direction wiring 83 comprises n pieces of wiring, that is,Dy1, Dy2, . . . , Dyn, and is 0.5 μm thick and 100 μm wide as similarlyformed as the X direction wiring 82.

[0185] There is an inter-layer insulation layer not shown in theattached drawings between the m pieces of X direction wiring 82 and npieces of Y direction wiring 83. They are electrically separated (m andn indicate positive integers).

[0186] The inter-layer insulation layer not shown in the attacheddrawings is configured by a 0.8 μm thick SiO₂ in the spatter method,etc. The thickness of the inter-layer insulation layer is determinedsuch that it can be formed in a desired shape on all or a part of thesubstrate 81 forming the X direction wiring 82, specifically such thatit is durable against the potential difference of the cross portionbetween the X direction wiring 82 and the Y direction wiring 83, thatis, the device capacity per device is 1 pF or smaller, and the devicedurability of 30 V according to the present embodiment.

[0187] The X direction wiring 82 and the Y direction wiring 83 are leadas external terminals.

[0188] A pair of electrodes (not shown in the attached drawings) formingthe electron-emitting device 84 electrically connected through m piecesof X direction wiring 82, n pieces of Y direction wiring 83, and theconnection line 85 comprising a conductive metal, etc.

[0189] According to the present embodiment, the Y direction wiring andthe X direction wiring are connected respectively as the cathodeelectrode side and the extraction electrode side.

[0190] The n pieces of Y direction wiring of Dy1, Dy2, . . . Dyn arecommonly grounded, the pulse voltage on the positive side to the groundis applied to Dx1, the electron-emitting device 84 of the row Dx1 isselected, and the equalizing process is performed.

[0191] Then, a similar voltage is applied to Dx2, the electron-emittingdevice 84 of the row Dx2 is selected, and the equalizing process isperformed. Similarly, the rows Dx3, Dx4, . . . , Dxm are selected toperform the equalizing process sequentially in the X direction.

[0192] The image-forming apparatus configured using the electron sourcein the simple matrix array is described below by referring to FIG. 9.FIG. 9 shows the display panel of the image-forming apparatus using sodalime glass as a glass substrate material.

[0193] In FIG. 9, reference numeral 81 denotes an electron sourcesubstrate for which a plurality of electron-emitting devices areprovided, reference numeral 91 denotes a rear plate to which theelectron source substrate 81 is fixed, and reference numeral 96 denotesa face plate in which the fluorescent film 94, the metal back 95, etc.are formed inside the glass substrate 93. Reference numeral 92 denotes asupport frame to which the rear plate 91 and the face plate 96 areconnected using frit glass, etc. Reference numeral 97 denotes anenvelope which is sealed by baking at the temperature of 450° C. in thevacuum for ten minutes.

[0194] Reference numeral 84 denotes an electron-emitting device. Xdirection wiring 82 and Y direction wiring 83 are connected to a pair ofdevice electrodes of an electron-emitting device. The respective rowwiring and column wiring of the X direction wiring 82 and the Ydirection wiring 83 are lead outside the envelope 97 as terminals ofDoxl to Doxm and Doyl to Doyn.

[0195] The envelope 97 comprises the face plate 96, the support frame92, and the rear plate 91 as described above. In the other hand, theenvelope 97 having sufficient strength against the atmosphere byproviding a support referred to as a spacer, but not shown in theattached drawings between the face plate 96 and the rear plate 91.

[0196] The metal back 95 performs a smoothing process (normally referredto as a “filming”) on the inner surface of the fluorescent film 94 afterproducing the fluorescent film 94, and then the vacuum evaporationprocess, etc. is performed, thereby piling Al.

[0197] To enhance the conductivity of the fluorescent film 94, the faceplate 96 is provided with a transparent electrode (not shown in theattached drawings) outside the fluorescent film 94.

[0198] Since the electron from the electron source is emitted to theextraction electrode 2 side according to the present embodiment, thefluorescent film 94 is provided in the position 200 μm shifted towardthe extraction electrode 2 when the anode voltage Va is 10 kV and theinter-anode distance H is 2 mm.

[0199] Thus, the obtained matrix electron source indicates equalcharacteristic for each electron-emitting device 84, and indicateslittle distribution of Ie, therefore it is desired as a display device,etc.

[0200] (Fourth Embodiment)

[0201] According to the present embodiment, an example of an equalizingprocess is performed for each electron-emitting device in the displaydevice as an image-forming apparatus comprising a matrix electron sourcefor which a plurality of electron-emitting devices are provided.

[0202] As in the third embodiment, the matrix electron source as shownin FIG. 8 is produced. According to the present embodiment, the Ydirection wiring 83 is connected to the cathode electrode, and the Xdirection wiring 82 is connected to the extraction electrode.

[0203] A voltage is applied to Dy1 and Dx1, the electron-emitting device84 at the cross portion between Dy1 and Dx1 is selected, and it isindependently driven and the equalizing process is performed.

[0204] Then, a similar voltage is applied to Dy1 and Dx2, theelectron-emitting device 84 at the cross portion between Dy1 and Dx2 isindependently selected, and the equalizing process is performed.Similarly, the equalizing process is performed sequentially on each ofthe electron-emitting devices 84.

[0205] Using the matrix electron source produced according to thepresent embodiment, the display device as shown in FIG. 9 is produced asin the third embodiment.

[0206] With the matrix electron source obtained as described above, thedistribution of Ie is further reduced, and is recommended as a displaydevice, etc.

[0207] As described above, according to the present invention, theshapes of a plurality of projections of the electron-emitting member 4are equalized. Therefore, a local field condensation is avoided on theelectron-emitting member, and the electron emission characteristic canbe equalized. Additionally, the local field condensation which causeshigh current density and an overload can be suppressed, thereby avoidingthe reduction of an emission current.

[0208] Therefore, the induction of discharge can be suppressed, thedurability of the electron-emitting device can be elongated, and astable electron emission current with a small fluctuation with time canbe maintained for a long period.

[0209] Furthermore, for an electron source and an image-formingapparatus provided with a plurality of electron-emitting devices, theelectron emission current of each electron-emitting device can be stablymaintained. Therefore, the durability of each pixel can be elongated,the brightness of an image can be successfully represented, and theflicker of an image can be avoided, thereby maintaining a constantdisplay characteristic for a long period.

What is claimed is:
 1. A method for producing an electron-emittingdevice, comprising the steps of: (A) disposing a cathode electrode on asurface of a substrate; (B) providing an electrode opposite the cathodeelectrode; (C) disposing plural pieces of fiber containing carbon as amain component on the cathode electrode; and (D) applying potentialhigher than potential applied to the cathode electrode underdepressurized condition to an electrode opposite the cathode electrode.2. The method for producing an electron-emitting device, according toclaim 1, wherein said electrode opposite the cathode electrode is ananode electrode provided apart the substrate.
 3. The method forproducing an electron-emitting device, according to claim 1, whereinsaid electrode opposite the cathode electrode is a leading electrodeprovided apart from the cathode electrode on the surface of thesubstrate.
 4. The method for producing an electron-emitting device,according to claim 1, wherein said step of applying potential to theelectrode opposite the cathode electrode is a step of increasing thenumber of emission sites.
 5. The method for producing anelectron-emitting device, according to claim 1, wherein said potentialapplied to the electrode opposite the cathode electrode is potential atwhich an electron is emitted from the fiber.
 6. The method for producingan electron-emitting device, according to claim 1, wherein said step ofapplying the potential to the electrode opposite the cathode electrodeis performed under condition of a gas chemically or physically reactiveto the fiber.
 7. The method for producing an electron-emitting device,according to claim 6, wherein said gas chemically reactive to the fiberis one of O₂, H₂, CO₂, and H₂O.
 8. The method for producing anelectron-emitting device, according to claim 6, wherein a pressure forintroducing the gas is equal to or over 1×10⁻⁴ Pa.
 9. The method forproducing an electron-emitting device, according to claim 6, whereinsaid step of applying the potential to the electrode opposite thecathode electrode is a step of applying a pulse voltage between thecathode electrode and the electrode opposite the cathode electrode. 10.The method for producing an electron-emitting device, according to claim1, wherein said fiber is formed by decomposing a hydrogen carbide gas.11. The method for producing an electron-emitting device, according toclaim 10, wherein said fiber is formed by decomposing the hydrogencarbide gas using a catalyst provided on the cathode electrode inadvance.
 12. The method for producing an electron-emitting device,according to claim 11, wherein said catalyst is one of Fe, Co, Pd, andNi, or an alloy consisting of materials selected from among Fe, Co, Pd,and Ni.
 13. The method for producing an electron-emitting device,according to claim 1, wherein said fiber is formed by graphitenanofiber, carbon nanotube, or amorphous carbon fiber.
 14. The methodfor producing an electron-emitting device, according to claim 1, whereinsaid fiber comprises a graphen.
 15. The method for producing anelectron-emitting device, according to claim 1, wherein said fibercomprises a plurality of graphens.
 16. The method for producing anelectron-emitting device, according to claim 15, wherein said pluralityof graphens are layered in an axial direction of the fiber.
 17. A methodfor producing an electron source obtained by arranging a plurality ofelectron-emitting devices, which are produced according to any of claims1 to
 16. 18. A method for producing an image-forming apparatus having anelectron source and an image-forming member, wherein said electronsource is produced in the method according to claim
 17. 19. A method forproducing an electron source having a plurality of electron-emittingdevices, comprising the steps of: (A) providing on a substrate aplurality of electron-emitting devices comprising plural pieces of fibereach containing carbon as a main component, and plural pieces of wiringelectrically connected to at least one of the plurality ofelectron-emitting devices; (B) measuring by applying a voltage to atleast a part of the plurality of electron-emitting devices, anelectrical characteristic of said at least a part of the plurality ofelectron-emitting devices to which the voltage is applied; (C) reducinga difference in electrical characteristic among the plurality ofelectron-emitting devices based on a measurement result, wherein saidstep of reducing the difference in characteristic among the plurality ofelectron-emitting devices comprising a step of emitting an electron fromat least one of the plurality of electron-emitting devices underdepressurized condition.
 20. The method for producing an electronsource, according to claim 19, wherein said plural pieces of wiringcomprises plural pieces of row direction wiring, and plural pieces ofcolumn direction wiring crossing the row direction wiring, and each ofthe electron-emitting devices is connected to one of the row directionwiring and one of the column direction wiring.
 21. The method forproducing an electron source, according to claim 20, wherein said stepof reducing the difference in characteristic among the plurality ofelectron-emitting devices contains a step of emitting an electron from adesired electron-emitting device by repeating a step of selecting fromsaid plural pieces of column direction wiring or said plural piece ofrow direction wiring, a part of the pieces of column direction wiring orrow direction wiring, and emitting an electron from an electron-emittingdevice connected to the selected wiring.
 22. The method for producing anelectron source, according to claim 19, wherein said step of reducingthe difference in characteristic among the plurality ofelectron-emitting devices contains a step of emitting an electron from adesired electron-emitting device by repeating a step of selecting a partof electron-emitting devices from among the plurality ofelectron-emitting devices and emitting an electron from the selectedelectron-emitting device.
 23. The method for producing an electronsource, according to claim 19, wherein: said electron-emitting devicecontains a cathode electrode to which the fiber is electricallyconnected, and a leading electrode provided apart from the cathodeelectrode; and said step of emitting an electron from theelectron-emitting device is performed by applying a voltage between thecathode electrode and the leading electrode.
 24. The method forproducing an electron source, according to claim 19, wherein said stepof emitting an electron from the electron-emitting device is performedby applying a voltage between the electrode provided apart from thesubstrate and the electron-emitting device.
 25. The method for producingan electron source, according to claim 19, wherein: saidelectron-emitting device contains a cathode electrode to which the fiberis electrically connected, and a leading electrode provided apart fromthe cathode electrode; and said step of emitting an electron from theelectron-emitting device is performed by applying a potential differencebetween an electrode provided apart from the substrate and theelectron-emitting device.
 26. The method for producing an electronsource, according to claim 19, wherein said step of reducing thedifference in characteristic among the plurality of electron-emittingdevices is a step of increasing the number of emission sites of at leastone electron-emitting device.
 27. The method for producing an electronsource, according to claim 19, wherein said step of reducing thedifference in characteristic among the plurality of electron-emittingdevices is performed in ambient of a gas chemically or physicallyreactive to the fiber.
 28. The method for producing an electron source,according to claim 27, wherein said gas chemically reactive to the fibercontains a gas selected at least from among O₂, H₂, CO₂, and H₂O. 29.The method for producing an electron source, according to claim 28,wherein a pressure for introducing the gas is equal to or over 1×10⁻⁴Pa.
 30. The method for producing an electron source, according to claim27, wherein said step of emitting an electron from the electron-emittingdevice is performed by applying a pulse voltage to the electron-emittingdevice.
 31. The method for producing an electron source, according toclaim 19, wherein said fiber is formed by decomposing a hydrogen carbidegas.
 32. The method for producing an electron-emitting device, accordingto claim 31, wherein said fiber is formed by decomposing the hydrogencarbide gas using a catalyst provided on the cathode electrode inadvance.
 33. The method for producing an electron-emitting device,according to claim 32, wherein said catalyst is one of Fe, Co, Pd, andNi, or an alloy consisting of materials selected from among Fe, Co, Pd,and Ni.
 34. The method for producing an electron-emitting device,according to claim 19, wherein said fiber is formed by graphitenanofiber, carbon nanotube, or amorphous carbon fiber.
 35. The methodfor producing an electron-emitting device, according to claim 19,wherein said fiber comprises a graphen.
 36. The method for producing anelectron-emitting device, according to claim 19, wherein said fibercomprises a plurality of graphens.
 37. An electron-emitting deviceaccording to claim 36, wherein said plurality of graphens are layered inan axial direction of the fiber containing carbon as a main component.38. A method for producing an image-forming apparatus having an electronsource and an electron-emitting member, wherein said electron source isproduced in the method according to any of claims 19 to
 37. 39. Themethod for producing an image-forming apparatus, according to claim 38,wherein said image-forming apparatus is obtained by seal bonding a firstsubstrate provided with the image-forming member with a second substrateprovided with the electron source; and an electrical characteristic ofthe electron-emitting device is measured before the first and secondsubstrates are seal bonded with each other.
 40. The method for producingan image-forming apparatus, according to claim 38, wherein saidimage-forming apparatus is obtained by seal bonding a first substrateprovided with the image-forming member with a second substrate providedwith the electron source; and said step of reducing the difference inelectrical characteristic among the plurality of electron-emittingdevices is performed before the first and second substrates are sealbonded with each other.